Fix TCPSocket::accept()

[SeppoTakalo]

Description

TCPSocket::accept() was actually always return NULL, and unsted because we only
have tests with one device.

We will add the testcase for this soon.

This fixes #7936

@kjbracey-arm please review

Pull request type

[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Breaking change

[SeppoTakalo]

Tested manually by modifying the TEST_APP from Mbed OS

diff --git i/TEST_APPS/device/socket_app/cmd_socket.cpp w/TEST_APPS/device/socket_app/cmd_socket.cpp
index 4aefe700d..0d321159f 100644
--- i/TEST_APPS/device/socket_app/cmd_socket.cpp
+++ w/TEST_APPS/device/socket_app/cmd_socket.cpp
@@ -1125,22 +1125,13 @@ static int cmd_socket(int argc, char *argv[])
         }
 
     } else if (COMMAND_IS("accept")) {
-        SocketAddress addr;
         int32_t id;
-        if (!cmd_parameter_int(argc, argv, "accept", &id)) {
-            cmd_printf("Need new socket id\r\n");
-            return CMDLINE_RETCODE_INVALID_PARAMETERS;
-        }
-        SInfo *new_info = get_sinfo(id);
-        if (!new_info) {
-            cmd_printf("Invalid socket id\r\n");
-            return CMDLINE_RETCODE_FAIL;
-        }
-        TCPSocket *new_sock = static_cast<TCPSocket *>(&new_info->socket());
-        nsapi_error_t ret = static_cast<TCPServer &>(info->socket()).accept(new_sock, &addr);
+        nsapi_error_t ret;
+        TCPSocket *new_sock = static_cast<TCPSocket &>(info->socket()).accept(&ret);
         if (ret == NSAPI_ERROR_OK) {
-            cmd_printf("TCPServer::accept() new socket sid: %d connection from %s port %d\r\n",
-                       new_info->id(), addr.get_ip_address(), addr.get_port());
+            SInfo *new_info = new SInfo(new_sock);
+            m_sockets.push_back(new_info);
+            cmd_printf("TCPServer::accept() new socket sid: %d\r\n", new_info->id());
         }
         return handle_nsapi_error("TCPServer::accept()", ret);
     }

[kjbracey]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3040
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7992/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Test : SUCCESS

Build number : 2813
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7992/2813

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2656
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7992/

[SeppoTakalo]

@kjbracey-arm @0xc0170 @cmonr This is ready for merge, but missing version labels.
Pull it into RC3 if there is still time.

Otherwise next patch

[cmonr]

Thanks @SeppoTakalo. We'll bring it into the 5.10.1 patch.
At this point, we're doing risk mitigation for RC3 PRs, and even though this PR looks like it should be ok to come in, this not having a test case makes me a bit uneasy.